Motor vehicle driving aid system

ABSTRACT

The system comprises: detector devices ( 1 ) operable to provide electrical signals indicative of the relative distance and relative speed of the motor vehicle (V) with respect to a fixed or moving obstacle (O) ahead, and a processing and control unit (ECU) connected to such detector devices ( 1 ) as well as to brake actuators ( 2 - 4 ) and arranged to cause activation of the brake actuators ( 2 - 4 ) to effect automatic emergency braking of the motor vehicle (V) when the relative distance between the motor vehicle (V) and an obstacle (O) ahead lies between a first predetermined limit value (d F ) equal to the minimum value at which it is still possible to avoid collision by braking and a preselected intermediate value (d E ) comprised between said first limit value (d F ) and a second limit value (d Ecrit ) which is less than the said first limit value (d F ) and is equal to the minimum relative distance value at which it is still possible to follow a path which avoids the obstacle (O), or when the relative distance (d R ) becomes less than said second limit value (d Ecrit ).

[0001] The present invention relates to a motor vehicle driving aidsystem, and in particular a system operable to avoid the occurrence ofaccidents or at least to limit their consequences, and in particularoperable to avoid collisions against obstacles ahead and prevent thevehicle leaving the road.

[0002] Numerous systems have already been proposed for automatic vehiclebraking. Such known systems tend essentially to cause automatic brakingof a motor vehicle only on the basis of the relative distance andrelative speed with respect to an obstacle ahead.

[0003] The object of the present invention is to provide an improvedmotor vehicle driving aid system provided with electrically-controlledbrake actuator means.

[0004] According to a first aspect of the invention this object isachieved with a system comprising

[0005] first detector means operable to provide electrical signalsindicative of the relative distance and relative speed of the motorvehicle with respect to a fixed or moving object ahead, and

[0006] processor and control means connected to the first and seconddetector means as well as to the said brake actuator means and arrangedto

[0007] cause activation of the brake actuator means to effect anautomatic emergency braking of the vehicle,

[0008] when the relative distance between the motor vehicle and anobstacle ahead is comprised between a first predetermined limit valuewhich is equal to the minimum value at which it is still possible toavoid collision by braking and a preselected intermediate value,comprised between said first limit value and

[0009] a second limit value, which is less than the said first limitvalue and is equal to the minimum value of the relative distance atwhich it is still possible to follow a path avoiding the obstacle,

[0010] or when said relative distance becomes less than said secondlimit value.

[0011] Further characteristics and advantages of the system according tothe invention will become apparent from the following detaileddescription given purely by way of non-limitative example, withreference to the attached drawings, in which:

[0012]FIG. 1 is a schematic representation of a motor vehicle providedwith a driving aid system according to the invention;

[0013]FIG. 2 is a schematic representation in plan view from above of asection of road travelled by a vehicle;

[0014]FIG. 3 is a block diagram of a part of the processing and controlsystem included in the driving aid system according to the invention;

[0015]FIG. 4 is a diagram in which the states of the control system forthe driving aid of the present invention are represented;

[0016]FIG. 5 is a flow diagram which illustrates the manner in whichvarious functions of the driving aid system according to the inventionoperate;

[0017]FIG. 6 is a block diagram which illustrates a further portion ofthe processing and control system for a driving aid system according tothe invention;

[0018]FIG. 7 is a diagram which illustrates the states of a controlsystem for the driving aid of the invention; and

[0019]FIG. 8 is a diagram which illustrates the states of an overallcontrol system for the driving aid according to the invention.

[0020] In FIG. 1 the reference V generally indicates a motor vehicleprovided with a driving aid system according to the invention.

[0021] As will become more clearly apparent hereinafter in thedescription, a driving aid system according to the invention can beformed in such a way that it is able to perform one or more of aplurality of functions. For each of these functions the driving aidsystem requires that the motor vehicle V be provided with a particularplurality of devices. Such devices can be shared for the performance ofdifferent functions.

[0022] With reference to FIG. 1 the devices necessary to have on boardthe vehicle V for the purpose of being able to perform all the functionswhich will be described hereinafter will now be described. It will,however, be clear from the following description, as well as from theattached claims, which devices are specifically necessary for theperformance of each specific function.

[0023] A first function performed by the driving aid system is that of“Emergency Braking”.

[0024] This function aims to avoid the collision of the motor vehiclewith a fixed or moving obstacle present in the path which it is justabout to follow. The function provides for automatic actuation of thevehicle brakes at a suitable distance evaluated with respect to theobstacle.

[0025] The function can involve the emission of an alarm signal toindicate to the driver the imminent risk situation and to stimulate him(or her) to take the necessary actions to avoid the collision. If thedriver does not intervene in the time necessary, for example, by beingdistracted or otherwise unable to act, the automatic braking occurs.

[0026] For actuation of the emergency braking function the motor vehicleV is provided with a frontal microwave radar apparatus 1, of thescanning type able to detect even stationary obstacles over apredetermined range of distances ahead of the motor vehicle. This radarapparatus is operable in particular to generate signals indicative ofthe relative speed V_(R) and relative distance d_(R) between the motorvehicle V and the possible obstacle ahead.

[0027] The frontal radar apparatus 1 is connected to an electronicprocessing and control unit ECU. The connection between the radarapparatus 1 and the unit ECU can be of direct type, that is to saydedicated, or can be achieved by means of a communications networkinstalled on board the motor vehicle V, such as, for example, the CANnetwork.

[0028] The motor vehicle V is provided, in a manner known per se, with abraking system including actuator devices 2 piloted by anelectro-hydraulic unit 3 in turn controlled by an electronic brakecontrol unit 4.

[0029] The unit 4 is also connected to the electronic control unit, ECU,directly or via an on board communications network such as the CANnetwork.

[0030] The electronic processing and control unit ECU is also connectedto a man-machine communications interface generally indicated 5.

[0031] A motor vehicle V is also provided with a steering column 6connected to a steering wheel 7.

[0032] The steering column 6 is associated with an electric controlactuator device 8 such as a DC electric motor, operable to causerotation under the control of an electronic steering control unit 9,also connected to the electronic processing and control unit ECU.

[0033] The steering column 6 further has an associated sensor 10operable to provide electrical signals indicative of the torque appliedto this shaft by the driver.

[0034] The unit ECU has further sensors connected to it, such as aposition sensor 11 associated with the brake control pedal, a positionsensor 12 associated with the accelerator pedal, and a position sensor13 operable to provide a signal indicative of the activation conditionof the direction indicators.

[0035] The reference numerals 14 and 15 in FIG. 1 indicate furthersensor devices operable to provide respective electrical signalsindicative of the speed of the motor vehicle and the speed of rotation,or number of revolutions in unit time, of the internal combustion engine(not illustrated) of the motor vehicle.

[0036] This motor vehicle V is moreover provided with a further seriesof sensors which, as will become more clearly apparent hereinafter, areable to provide electrical signals usable to evaluate the possibility offollowing an avoidance course for avoiding an obstacle ahead. In theexemplary embodiment illustrated these sensors comprise at least onevideo camera 16 directed towards the area ahead of the motor vehicle, aseries of lateral short-range radar systems 17 and a pair of videocameras 18 for monitoring the rear-side areas known as “blind spots”.

[0037] In the exemplary embodiment illustrated the motor vehicle V isprovided with two short-range radars 17 on each side, and a furthershort-range radar to cover the connection region of each side to thefront of the motor vehicle.

[0038] The video camera or cameras 16, the short-range radars 17, andthe video cameras 18 can be connected by means of interface devices tothe processing and control unit ECU or alternatively can be connected torespective signal processing units in turn connected to the processingand control unit ECU.

[0039] The motor vehicle V of FIG. 1 is further provided with a reardetector or sensor device 20 also connected to the processing andcontrol unit ECU to provide this latter with signals indicative of thepresence and relative distance, as well as the relative speed ofvehicles overtaking from behind the motor vehicle V. The detector orsensor 20 can be, for example, a microwave radar, or a lidar or amicro-video camera.

[0040] Several functions which can be performed by means of a drivingaid system according to the invention, and in particular the followingfunctions, will now be described:

[0041] emergency braking and possible obstacle avoidance,

[0042] control of the longitudinal dynamics of the vehicle; and

[0043] road lane maintenance.

[0044] Emergency Braking and Possible Obstacle Avoidance

[0045] In FIG. 2 of the attached drawings there is shown a section oftwo-way roadway W having two lanes for each direction, indicated L1, L2,L3 and L4 respectively. In this figure there is shown a motor vehicle Vtravelling in the lane L1 in the direction towards the right as seen inthe drawing.

[0046] An obstacle ahead of the vehicle V is indicated O. In the exampleillustrated the obstacle O is fixed, but as will be easily appreciated,the following considerations are valid also in relation to a possiblemoving obstacle, for example a motor vehicle proceeding in the samedirection.

[0047] In order to activate the emergency braking function theprocessing and control unit ECU of the motor vehicle V is set up todetect the presence of the obstacle O by means of the informationprovided by the frontal radar 1. This radar makes it possible inparticular to detect the relative distance d_(R) between the motorvehicle V and the obstacle O, and also their relative speed V_(R) as thedifference between the speed (possibly nil) of the obstacle and that ofthe motor vehicle.

[0048] As soon as the unit ECU detects that the relative speed V_(R)between the motor vehicle and the obstacle O becomes negative (obstacleapproaching) this unit provides for dynamic evaluation of the minimumdistance d_(F) at which the braking system of the motor vehicle V mustintervene automatically in order to perform automatic emergency brakingif collision with the obstacle is to be avoided.

[0049] The unit ECU can be arranged to calculate the distance d_(F) as afunction of the (known) reaction times of the braking system, as well asthe braking power which is at the moment still available, thisinformation being providable to the unit ECU from the electronic unit 4which supervises the braking system. The distance d_(F) can further becalculated as a function of the ground-adhesion conditions which in amanner known per se can be detected by a suitable sensor (notillustrated), or can be indicated to the motor vehicle V from anyroadway infrastructures (not illustrated) which may be available, or canbe communicated from other vehicles.

[0050] The unit ECU can finally be arranged to calculate the distanced_(F) in relation to different levels of braking power to be applied inthe possible emergency braking operation depending on a preliminarysetting made by the vehicle user.

[0051] In each case, when the relative distance d_(R) approaches thecalculated distance d_(F) the unit ECU can, via the man-machineinterface 5 provide an alarm indication to the motor vehicle driver,signalling to him the risk situation and stimulating him to activate thebrakes so as to avoid the collision. If, however, the driver does notact in a suitable time, perhaps because of being distracted or unable todo so, the unit ECU triggers the automatic emergency braking, providingfor this purpose corresponding signals to the electronic unit 4 whichsupervises the braking system.

[0052] Situations can however occur in which the relative distance d_(R)between the motor vehicle V and obstacle O ahead is or becomes less thanthe distance d_(F) in circumstances where it may be in general stillpossible to avoid collision with the obstacle O by performing a lateralavoidance manoeuvre. In FIG. 2 the reference d_(E) indicates anintermediate value of the relative distance, less than d_(F), startingfrom which, being it no longer possible to avoid the collision only bybraking, it is attempted to avoid the collision—if possible—byperforming a L lateral obstacle-avoidance manoeuvre. The value of d_(E)is preselected on the basis of the characteristics of the motor vehicle.In the same FIG. 2, d_(Ecrit) indicates the relative distance less thanwhich it is no longer possible to avoid collision with the obstacle O,not even by effecting an avoidance manoeuvre.

[0053] If the relative distance d_(R) is less than d_(Ecrit) the unitECU, via the braking control unit 4, controls the emergency braking atthe maximum braking power available, for the purpose of reducing theinevitable collision damage to the minimum.

[0054] The obstacle-avoidance function performed by the driving aidsystem according to the invention, sets out to allow lateral avoidanceof an obstacle which appears, even unexpectedly, in the path of themotor vehicle, preventing the normal continuance of travel in the samelane.

[0055] The automatic obstacle-avoidance manoeuvre is convenientlypreceded by an alarm signal provided to the motor vehicle driver via theman-machine interface 5.

[0056] If the driver does not intervene immediately, for example becauseof being distracted or otherwise being unable to act, or if theavailable intervention time, taking into consideration the averagereaction times of a driver, would make a manual obstacle-avoidancemanoeuvre too late and therefore ineffective, the unit ECU is operableto assume control of the motor vehicle and to pilot the actuation of anobstacle avoidance manoeuvre in a totally automatic manner bycontrolling the steering actuator 8 associated with the steering columnvia the steering control unit 9 for the purpose of modifying the path ofthe vehicle for example in the manner indicatively illustrated by thechain line E in FIG. 2. The driver can always be informed about theprogress of the manoeuvre by the man-machine interface 5, and candecide, if he so wishes, to interact with the automatic avoidancefunction.

[0057] The preliminary and necessary condition for actuation of anautomatic obstacle-avoidance manoeuvre is that the set of signalsprovided by the short-range radar 17 and the video cameras 18 and 20 beindicative of the effective availability of a collision-avoidance pathwhich allows the motor vehicle to avoid the obstacle by passing it tothe left or to the right without colliding with other obstacles orvehicles overtaking from behind and without leaving the carriageway.

[0058] The processing and control unit ECU is therefore arranaged toevaluate if the manoeuvre is achievable, or rather if a possibleavoidance path exists. If so, and if the driver does not intervene, theunit ECU activates the obstacle avoidance function.

[0059] If the road has lanes delimited by continuous broken or paintedlateral strips, during the avoidance manoeuvre the unit ECU cancalculate the transverse position of the motor vehicle by means of dataprovided to it from the frontal video camera 16 which provides imagesfrom which it is possible to deduce the position of the vehicle withrespect to the said lane demarcation lines, both in terms of distanceand angle relative to the instantaneous path of the motor vehicle.

[0060] In the absence of lane demarcation lines the position of themotor vehicle can be reconstructed by the unit ECU by means of othersensors, for example a gyroscope and an accelerometer providinginformation on the yaw rate and lateral acceleration of the motorvehicle, and/or on the basis of information concerning the position ofthe motor vehicle which can be deduced from the signals provided by thefrontal radar 1 and the lateral short-range radar 17.

[0061] An avoidance manoeuvre can be considered concluded from themoment the motor vehicle is displaced laterally by an amount sufficientto avoid the obstacle.

[0062] In a possible alternative, the obstacle-avoidance manoeuvre caninstead be completed with a further manoeuvre back to the lane fromwhich the vehicle started, obviously preceded by an analysis of the areasurrounding the motor vehicle to evaluate the availability of thismanoeuvre.

[0063] In FIG. 3 there is schematically illustrated the architecture ofthe control system for performing the obstacle-avoidance function. Forthis purpose the system comprises a motor vehicle positionreconstruction unit 21 which receives information provided from thevarious sensors involved for the performance of the function. Thereconstruction unit 21 provides output signals indicative of thetransverse position y of the motor vehicle, for example in a co-ordinatesystem in which, as is schematically illustrated in FIG. 2, the x-axiscoincides with the direction of forward movement of the vehicle, and they-axis is a horizontal axis transverse the x-axis, passing through thecentre of gravity of the motor vehicle.

[0064] At least some of the said sensors are moreover connected to areference generator 22 which, following detection of the characteristicsof the manoeuvring area, generates the profile or shape of an avoidancemanoeuvre which the vehicle must possibly follow. This avoidance profileis substantially generated as a sequence of transverse positionreference values y_(ref) In order to calculate y_(ref) the generator 22takes into account both the relative speed between the motor vehicle andthe obstacle and the position of the obstacle in the transverse sense.

[0065] The outputs of the position reconstruction unit 21 and thegenerator 22 are connected to the inputs of a controller 23 whichgenerates signals indicative of the required steering angle α_(r)necessary to follow the avoidance profile produced by the generator 22.

[0066] The output of the controller 23 is connected to the steeringcontrol unit 9 which pilots the steering actuator 8.

[0067] The logic for management of the emergency braking and obstacleavoidance functions can be described by means of a state machine which,as is schematically illustrated in FIG. 4, comprises three statesindicated as:

[0068] rest or “idle” state;

[0069] obstacle avoidance state; and

[0070] emergency braking state.

[0071] In FIG. 4 the said three states are represented with three“bubbles” indicated 101, 102 and 103. In FIG. 4 the transitions from onestate to the other are indicated by arrows on which are superimposedrespective blocks within which the conditions in which the respectivestate transition takes place are summarised.

[0072] The diagram of FIG. 4 is essentially self-explanatory and willnot therefore be further described.

[0073] Finally, in FIG. 5 there is presented a flow diagram whichillustrates, likewise in a self-explanatory manner, the conditionsessential for performing the emergency braking and obstacle avoidancefunctions.

[0074] Longitudinal Dynamic Control Function

[0075] As will appear more clearly hereinafter, the longitudinal dynamiccontrol function of the motor vehicle (hereinafter generally calledLongitudinal Control) essentially provides for integration of twosub-functions which will be defined “adaptive cruise speed control” inthe Anglo-Saxon terminology, and “stop-and-go”. This longitudinalcontrol function has the object of assisting the driver by controllingthe cruise speed of the motor vehicle or the safety distance withrespect to the preceding vehicle along its path.

[0076] The said function is primarily actuated on the basis ofinformation on the relative velocity V_(R) and distance d_(R) providedby the frontal radar 1 as well as the sensors 14 and 15 which providesignals indicative of the speed V_(F) of the motor vehicle and the speedof rotation rpm of the motor vehicle engine.

[0077] The adaptive cruise control function of the cruise speedrepresents an extension of the traditional cruise speed control functionand, therefore, as well as achieving and maintaining a speed set by thedriver, is able to adapt the speed of the vehicle to that of thepreceding motor vehicle with limited accelerations and decelerations.

[0078] The stop-and-go function represents an extension of the adaptivecruise speed control at low speeds in such a way as to be able to assistthe driver even in urban traffic areas or when reversing.

[0079] As is shown in the block diagram of FIG. 6, the processing andcontrol unit ECU which supervises the performance of the longitudinalcontrol functions is connected to sensors 11 and 12 associated with thebrake pedal and the accelerator pedal respectively. Each intervention onthe brake pedal causes the function to be disabled, reinstating drivercontrol of the motor vehicle, whilst pressure exerted on the acceleratorpedal allows the set reference speed to be exceeded without necessarilydisabling the function.

[0080] For setting the desired cruise speed or the desired safetydistance the unit ECU is connected to respective manually-operatedsetting devices indicated 25 and 26 in FIG. 6.

[0081] As will appear more clearly hereinafter, for management of thisfunction, the processing and control unit ECU is arranged to send themotor vehicle engine management unit 19 a signal T_(R) indicative of therequired torque value generated by the motor vehicle engine, or a signalB to the brake control unit 4, signal B being indicative of the requiredbraking intensity. With reference to the block diagram of FIG. 6, whichshows a possible control architecture, the signals provided by thesensors 14 and 15, as well as the signals provided by the frontal radar1 arrive at an observer block 30. In this block signals are filteredwith respect to noise and, if necessary, reconstructed.

[0082] The observer block 30 provides filtered signals {circumflex over(V)}_(F), {circumflex over (V)}_(R) and {circumflex over (d)}_(R) to areference signal generator 31 which also receives the indication of thedesired cruise speed v_(cc) or the desired safety distance d_(s) toachieve and then maintain essentially constant.

[0083] The generator 31 is arranged to generate a reference signala_(xref) indicative of the relative longitudinal acceleration of themotor vehicle V as a function of the speed of the motor vehicle, thespeed of rotation of the engine, the set value of the vehicle speed andthe safety distance with respect to the preceding vehicle, as well asthe relative distance and speed with respect to the obstacle ahead.

[0084] This signal is provided on the one hand to an input of acompensator block or feedback control 32, and on the other to an inputof a summing unit 33. The compensator block 32 has a further input whichreceives the signal {circumflex over (V)}_(F) from the observer block30.

[0085] The compensator block 32 is arranged to perform a feedbackcontrol, for example, of proportional-integral type, and to provide inthis case an output compensation signal a_(xcomp) essentiallyproportional to the integral of the difference between the relativelongitudinal acceleration a_(xref) and the instantaneous longitudinalacceleration a_(F) of the motor vehicle, this latter being calculated asthe integral of the signal {circumflex over (V)}_(F).

[0086] The output of the compensator block 32 is connected to a secondinput of the summing unit 33, which in operation therefore provides asoutput signal a_(xreq) corresponding to the sum of the signals a_(xref)and a_(xcomp), as an acceleration demand signal representative of therequired longitudinal acceleration of the motor vehicle V to achieve ormaintain the set cruise speed value or safety distance.

[0087] The output of the summing unit 33 is connected to an input of acontrol and piloting block 34 arranged to generate, on the basis of apredetermined mathematical model of the motor vehicle, the signals T_(r)and B for control of the torque generated by the engine of the motorvehicle and, respectively, of the motor vehicle brakes, as a function ofthe speed of the vehicle and the speed of rotation of the engine, aswell as the said longitudinal acceleration demand signal a_(xreq).

[0088] The longitudinal dynamic control function of the motor vehiclecan be achieved a state machine, for example in accordance with thefive-state scheme shown in FIG. 7. This machine essentially provides thefollowing states, identified in FIG. 7 with numerals 201, 205:

[0089] “Rest or Idle” 201: the longitudinal control function isdisabled; return to this state from all the other states 202 to 205 fromthe moment the driver actuates the brake pedal, or inhibits thefunction, for example by acting on a suitable switch;

[0090] “Override” state 202: the transitions to this state take place ifone of the following conditions occur;

[0091] 1) there is a gear change in progress (clutch open or “on”) andsimultaneously the driving aid system is not yet requesting interventionof the braking system;

[0092] 2) the driver presses the accelerator pedal: the function is puton standby and the control of the motor vehicle is returned to thedriver.

[0093] “Cruise” or “speed control” state 203: in this state the systemtends to achieve and then maintain the cruise speed V_(cc) set by thedriver;

[0094] “Track” or “distance control” state 204: the system tends toachieve and maintain the safety distance d_(s) set by the driverrelative to the preceding vehicle; and

[0095] “Stop” state 205: a state in which the control is momentarily“frozen” and the motor vehicle is maintained stationary.

[0096] The labels which in FIG. 7 are superimposed over the transitionarrows generally indicate in a self-explanatory manner the conditionsfor passage from one state to another.

[0097] The captions in these labels have essentially the followingsignifications:

[0098] ACC=ON: adaptive control function of the cruise speed turned on;

[0099] S&G=ON: Stop-and-Go function turned on;

[0100] Accelerator=ON: accelerator pedal pressed;

[0101] Brake=ON: brake pedal pressed;

[0102] Clutch=ON: clutch open;

[0103] Obstacle Absence/Presence: absence or presence of obstacleindicated by the frontal radar 1 in the path of the vehicle;

[0104] New v_(cc): new value of cruise speed set;

[0105] New d_(s): new safety distance set;

[0106] New obstacle: detection of a new obstacle.

[0107] Lane Maintenance Function

[0108] This function will find wide approval from those who, for variousreasons, are constrained to utilise the motor vehicle as a means oftransport for a large number of hours and on long journeys.

[0109] This function, by characteristics which will be illustrated,belongs both to the family of driving aid functions in that it serves toalleviate the tension load which a driver experiences after a long timedriving a motor vehicle, but at the same time also belongs to the familyof preventive safety functions since it guarantees a good margin ofsafety in relation to actions consequent on distractions or temporarylapses of the driver.

[0110] This function allows, as will be seen, for the vehicle to beautomatically returned to the lane in which it had been travellingwithout any direct intervention from the steering wheel by the driver.

[0111] The function is actuated by utilising the information provided byvision sensors such as the video camera 16, with associatedimage-processing devices operable to analyse the geometry of the roadahead of the vehicle in motion and its position with respect to thelateral limits of the lane in which it is travelling.

[0112] The correction, where necessary, of the path of the motor vehicleis achieved by means of the steering actuator 8 with a feedback controlbased on the information from the sensor 10 associated with the steeringcolumn 6.

[0113] The control architecture can include essentially an observer,which on the basis of the information provided from the sensor 10associated with the steering column reconstructs the lateral position ofthe vehicle within the ambit of the lane and estimates the statesnecessary for a closed loop position controller. This controller, whichsupervises the lateral displacement of the vehicle, compares theinformation coming from the observer with that coming from a referencegenerator prearranged to generate a comfortable path or profile whichthe motor vehicle must follow to bring it from the instantaneousposition towards the centre of the lane in which the vehicle istravelling. The lateral displacement controller generates at its outputa signal indicative of the steering angle necessary to bring the motorvehicle to the centre of the lane. This signal is imparted to thesteering control unit 9 which correspondingly pilots the steeringactuator 8.

[0114] Conveniently, the lane maintenance function is of co-operativetype in the sense that action exerted by the control system iscompatible with the natural inclination to manual guidance by thedriver. In other terms, the system allows the driver to guide the motorvehicle manually whenever the system recognises the intention of thedriver to wish to move the vehicle away from the ideal zone (roadcentre) in which it seeks to maintain the motor vehicle.

[0115] To this end the processing control unit which supervises thefunction is conveniently arranged to reduce the weight of the controlaction when the driver applies a torque greater than a predeterminedvalue to the steering column and/or to interrupt the control action whenthe driver activates a direction indicator.

[0116] In a variant the co-operative lane maintenance function can becombined with traffic monitoring to the side and behind the vehicle bymeans of sensors such as, for example, the lateral radar 17 and thevideo cameras 18, and the processing and control unit ECU can bearranged to pilot the steering actuator means in such a way that theseresist, by applying opposing torque to the steering shaft 6,displacements caused by the driver which would bring it into collisionwith overtaking vehicles or with lateral obstacles. The resisting torquecan be modulated as a function of the degree of risk of the manoeuvre.

[0117] Overall Anti-Collision Function

[0118] The integration and the synergy of previously-described functionsmakes it possible to achieve an overall or global anti-collision systemto increase the safety on board the motor vehicle by avoiding, inemergency conditions, collision with an obstacle or by limiting theconsequences of a possible collision.

[0119] The elementary functions of the driving aid usable to achieve asystem of this type are as follows:

[0120] Emergency Brake:

[0121] Obstacle Avoidance;

[0122] Lane Maintenance;

[0123] Longitudinal Control; and

[0124] Emergency Brake and Lane Maintenance.

[0125] On the basis of signals from the sensor system (radar 1,short-range radar 17, video cameras, etc), as well as from the enginemanagement unit, steering unit, gearbox, brakes and the man-machineinterface 5. The system is able to monitor the area around the vehicle Vand to cause intervention of the function which is best adapted, interms of safety, to the detected scenario. The system is then able torecognise a dangerous scenario, for example in which an obstacle impedesthe progress of the vehicle, to signal this to the driver and, in theevent of the driver not intervening, to automatically enable the mostsuitable emergency functions.

[0126] The co-operative lane maintenance function, combined with themonitoring of the area surrounding the motor vehicle can be convenientlyalways active. The other functions may, on the other hand, beselectively activated or de-activated by the driver.

[0127] In the diagram of the states shown in FIG. 8 the functions arerepresented by bubbles, whilst the conditions of passing from one stateto the other are represented by transition arrows.

[0128] In the diagram of FIG. 8 appears a bubble 301 corresponding tothe Rest or “Idle” state, a bubble 302 corresponding to the EmergencyBrake state, a bubble 303 corresponding to the “Obstacle Avoidance”state, and a bubble 304 corresponding to the “Longitudinal Control”state, a bubble 305 corresponding to the “Lane Maintenance” state. Aswell as these bubbles, the diagram of FIG. 8 shows a bubble 306denominated “Longitudinal Control and Lane Maintenance”, in which the“Longitudinal Control” and “Lane Maintenance” functions can beconsidered as a single state inasmuch as they are both enabled. In fact,the signals for actuation of Longitudinal Control and Lateral Control donot ever come into conflict with one another and it is thereforepossible to operate a control strategy which involves simultaneouslyacting on the engine, the braking system and the steering system.

[0129] In the diagram of FIG. 8 there is a further bubble 307denominated “Emergency Brake and Lane Maintenance” for this bubblesimilar considerations to those explained above in relation to thebubble 306 apply.

[0130] All the transitions of the state machine of FIG. 8 will now bedescribed, which transitions essentially describe all the possiblescenarios which can occur during a normal journey of a motor vehicle.

[0131] In FIG. 8 the labels relating to each transition have anassociated number which represents the priority of the transition itselfwith respect to all those which exit from the same state underexamination.

[0132] In the conditions described hereinafter both the signals from theman-machine interface 5 and those from the various sensors or detectorsor their processing are taken into account.

[0133] The various states and associated transitions will now bedescribed.

301—Rest or Idle State

[0134] In this state the system, whilst monitoring the scenario, doesnot intervene on the actuators. From this state the followingtransitions are possible.

[0135] 301.1—Transition to the Emergency Braking State

[0136] If the sensing system identifies a dangerous obstacle in the lanein which the vehicle is travelling, at a distance less than anintervention limit distance calculated according to a pre-establishedmanner, and if, moreover, the relative speed is negative and the maximumbraking power available makes it possible to avoid the collision, ordoes not make it possible to avoid it but there is no possibility of perse forming a lateral avoidance manoeuvre, then it passes to theemergency braking state.

[0137] 301.2—Transition to the Emergency Braking and Lane MaintenanceState

[0138] If the sensing system is able to detect the geometry of the lanein which the vehicle is travelling and if in this lane there has beenidentified an obstacle at a distance less than the said interventiondistance, and if the relative velocity is negative and the maximumavailable braking power allows collision avoidance, or does not allowavoidance but there is no possibility of a lateral avoidance manoeuvre,then it passes to the Emergency Braking plus Lane Maintenance state.

[0139] 301.3—Transition to the Obstacle Avoidance State

[0140] If the sensing system has identified an obstacle in the lane inwhich the vehicle is travelling, at a distance less than the saidintervention distance, and if the relative speed is negative and themaximum available braking power does not allow collision avoidance andthe possibility of performing a lateral avoidance manoeuvre exists, thenit passes to the Obstacle Avoidance state.

[0141] 301.4—Transition to the Longitudinal Control and Lane MaintenanceState

[0142] If the sensing system is able to detect the geometry of the lanein which the vehicle is travelling, and the driver has requested theLongitudinal Control function, it passes to the Longitudinal Controlplus Lane Maintenance state.

[0143] 301.5—Transition to the Lane Maintenance State

[0144] If the sensing system is able to detect the geometry of the lanein which the vehicle is travelling, it passes from the idle state to theLane Maintenance state.

[0145] 301.6—Transition to the Longitudinal Control State

[0146] If the driver has selected the Longitudinal Control function itpasses to the Longitudinal Control state.

302—Emergency Braking State

[0147] 302.1—Transition to the Idle State

[0148] If the emergency braking is terminated (because a relative speedgreater than or equal to zero has been reached and the relative distancehas become greater than the intervention distance) it passes to the Idlestate.

[0149] 302.2—Transition to the Obstacle Avoidance State

[0150] If during emergency braking the system detects that, following avariation in the distance and relative speed conditions of the obstacle,the maximum braking power is not sufficient to avoid the collision, itexecutes a transition to the Obstacle Avoidance state if the possibilityof executing a lateral manoeuvre still exists.

303—Obstacle Avoidance State

[0151] 303.1—Transition to the Idle State

[0152] If the obstacle avoidance is terminated, the calculated avoidancepath having been followed, it passes to the Idle state.

304—Longitudinal Control State

[0153] 304.1—Transition to the Idle State

[0154] If the user de-activates the Longitudinal Control function itpasses to the Idle state.

[0155] 304.2—Transition to the Emergency Braking plus Lane MaintenanceState

[0156] If the sensing system is able to determine the geometry of thelane in which the vehicle is travelling, and if an obstacle has beendetected in this lane at a distance less than the intervention distance,and the relative speed is negative and the maximum available brakingpower allows collision avoidance, or does not allow it but thepossibility of executing a lateral avoidance manoeuvre does not exist,then it passes to the Emergency Braking plus Lane Maintenance state.

[0157] 304.3—Transition to the Emergency Braking State

[0158] If the sensing system has identified an obstacle in the lane inwhich the vehicle is travelling at a distance less than the interventiondistance, and if the relative speed is negative and the maximumavailable braking power allows collision avoidance, or does not allowcollision avoidance but the possibility of effecting a lateral avoidancemanoeuvre does not exist, then it passes to the Emergency Braking state.

[0159] 304.4—Transition to the Obstacle Avoidance State

[0160] If the sensing system has identified an obstacle in the lane inwhich the vehicle is travelling, at a distance less than theintervention distance, and if the relative speed is negative and themaximum available braking power does not allow collision avoidance butthe possibility of executing a lateral avoidance manoeuvre exists, thenit passes to the Obstacle Avoidance state.

[0161] 304.5—Transition to the Longitudinal Control plus LaneMaintenance State

[0162] If the sensing system is able to detect the geometry of the lanein which the vehicle is travelling, it passes to the LongitudinalControl plus Lane Maintenance state.

305—Lane Maintenance State

[0163] 305.1—Transition to the Idle State

[0164] If the sensing system is not able to detect the geometry of thelane in which the vehicle is travelling it passes to the Idle state.

[0165] 305.2—Transition to the Emergency Braking plus Lane MaintenanceState

[0166] If the sensing system is able to detect the geometry of the lanein which the vehicle is travelling and if an obstacle in the lane hasbeen identified at a distance less than the intervention distance, andthe relative speed is negative and the maximum available braking powerallows collision avoidance, or does not allow collision avoidance butthe possibility of effecting a lateral avoidance manoeuvre does notexist, then it passes to the Emergency Braking plus Lane Maintenancestate.

[0167] 305.3—Transition to the Emergency Braking State

[0168] If the sensing system has identified an obstacle in the lane inwhich the vehicle is travelling at a distance less than the interventiondistance, if the relative speed is negative, and the maximum availablebraking power allows collision avoidance, or does not allow collisionavoidance but the possibility of effecting a lateral avoidance manoeuvredoes not exist, then it passes to the Emergency Braking state.

[0169] 305.4—Transition to the Obstacle Avoidance State

[0170] If the sensing system has identified an obstacle in the lane inwhich the vehicle is travelling, at a distance less than theintervention distance, and if the relative speed is negative and themaximum available braking power does not allow collision avoidance, butthe possibility of executing a lateral avoidance manoeuvre exists, thenit passes to the Obstacle Avoidance state.

[0171] 305.5—Transition to the Longitudinal Control plus LaneMaintenance State

[0172] If the user activates the Longitudinal Control function it passesto the Longitudinal Control plus Lane Maintenance state.

306—Longitudinal Control plus Lane Maintenance State

[0173] 306.1—Transition to the Idle State

[0174] If the sensing system is not able to detect the geometry of thelane in which the vehicle is travelling and if the user de-activates theLongitudinal Control function it passes to the Idle state.

[0175] 306.2—Transition to the Emergency Braking plus Lane MaintenanceState

[0176] If the system is able to detect the geometry of the lane and ifan obstacle in the lane has been identified at a distance less than theintervention distance, and if the relative speed is negative and themaximum available braking power allows collision avoidance, or does notallow collision avoidance and the possibility of executing a lateralavoidance manoeuvre does not exist, then it passes to the EmergencyBraking plus Lane Maintenance state.

[0177] 306.3—Transition to the Emergency Braking State

[0178] If an obstacle has been identified in the lane in which thevehicle is travelling at a distance less than the intervention distance,and if the relative speed is negative and the maximum available brakingpower allows collision avoidance, or does not allow collision avoidanceand the possibility of effecting a lateral avoidance manoeuvre does notexist, then it passes to the Emergency Braking state.

[0179] 306.4—Transition to the Obstacle Avoidance State

[0180] If an obstacle has been identified in the lane in which thevehicle is travelling, at a distance less than the interventiondistance, and if the relative speed is negative and the maximumavailable braking power allows collision avoidance and the possibilityof executing a lateral avoidance manoeuvre exists, then it passes to theObstacle Avoidance state.

[0181] 306.5—Transition to the Longitudinal Control State

[0182] If the sensing system is not able to detect the geometry of thelane in which the vehicle is travelling it passes to the LongitudinalControl state.

[0183] 306.6—Transition to the Lane Maintenance State

[0184] If the user deactivates the Longitudinal Control function itpasses to the Lane Maintenance state.

307—Emergency Braking plus Lane Maintenance State

[0185] 307.1—Transition to the Idle State

[0186] If the Emergency Braking is terminated (because a relative speedgreater than or equal to zero is achieved and the relative distance hasbecome greater than the intervention distance) it passes to the Idlestate.

[0187] 307.2—Transition to the Obstacle Avoidance State

[0188] If during emergency braking the maximum braking power is notsufficient, upon a variation in the distance and relative speedconditions of the obstacle, to avoid the collision, it passes to theObstacle Avoidance state if the possibility of executing a lateralavoidance manoeuvre still exists.

[0189] Naturally, the principle of the invention remaining the same, theembodiments and details of construction can be widely varied withrespect to what has been described and illustrated clearly by way ofnon-limitative example, without by this departing from the ambit of theinvention as defined in the attached claims.

1. A driving aid system (V) for a motor vehicle provided withelectrically-controlled brake actuator means (2-4), the aid systemcomprising: first detector means (1) operable to provide electricalsignals indicative of the relative distance and relative speed of the ofthe motor vehicle (V) with respect to a fixed or moving obstacle (O)ahead, and first sensor means (14, 15) operable to provide signalsindicative of the longitudinal speed of the motor-vehicle, andprocessing and control means (ECU) connected to the said first detectormeans (1) as well as to the said brake actuator means (2-4) and arrangedto detect the occurrence of a first operating condition in which therelative distance (d_(R)) between the motor vehicle (V) and the obstacle(O) ahead is comprised between a first predetermined limit value(d_(F)), equal to the minimum value at which it is still possible toavoid the collision by braking and a preselected intermediate value(d_(E)), comprised between said first limit value (d_(F)) and a secondlimit value (d_(Ecrit)) which is less than the said first limit value(d_(F)) and is equal to the minimum relative distance at which it isstill possible to follow an avoidance path around the obstacle (O); anda second operating condition in which the relative distance (d_(R)) isless than said second limit value (d_(Ecrit)); and cause activation ofthe said brake actuator means (2-4) to effect an automatic emergencybraking of the motor vehicle (V) upon the occurrence of one of saidoperating conditions; the system being characterised in that the saidprocessing and control means (ECU) are further coupled to an electroniccontrol system (19) for the propulsion means of the motor vehicle, andare operable, on the basis of signals provided from the said firstdetector means (1), to effect control of the longitudinal speed ofadvance of the motor vehicle (V) in such a way as to tend to maintainthe longitudinal speed of the motor vehicle at a predetermined valuewhen the said first detector means (1) do not indicate an obstacle aheadwithin a predetermined range or, selectively, the relative distance withrespect to a vehicle ahead proceeding in the same direction, when thefirst detector means (1) indicate the presence thereof within apredetermined range; said first sensor means (14, 15) being operable toalso provide signals indicative of the speed of rotation of the engineof the motor-vehicle; the said processing and control means (ECU)including reference signal generator means (31) coupled to the saidfirst sensor means (14, 15) and to the said first detector means (1) andarranged to generate a reference signal (a_(xref)) indicative of therelative longitudinal acceleration for the motor vehicle (V) as afunction of the distance and relative speed with respect to the obstacleahead, the longitudinal speed of the motor vehicle and the speed ofrotation of the engine as well as the set value of the speed of advanceof the vehicle or of the safety distance relative to a preceding vehicle(V); feedback control means (32) connected to the said reference signalgenerator means (31) and arranged to provide an output compensationsignal (a_(xcomp)) which is a function of the difference between therelative acceleration signal (a_(xref)) and the instantaneouslongitudinal acceleration (a_(F)) of the motor vehicle (V); summingmeans (33) operable to provide an output acceleration demand signal(a_(xreq)) for the motor vehicle, essentially proportional to the sum ofthe said reference signal (a_(xref)) and the compensation (a_(xcomp)),and piloting and control means (34) operable to generate, on the basisof a predetermined mathematical model of the motor vehicle (V), controlsignals (T_(R); B) of the torque generated by the motor vehicle and/orof the motor vehicle braking intensity as a function of the longitudinalspeed of the vehicle, the speed of rotation of the engine and the saidlongitudinal acceleration demand signal (a_(xreq)).
 2. A systemaccording to claim 1, in which the said processing and control means(ECU) are further arranged to activate signalling means (5) operable toprovide the driver with an indication of the opportunity of performing alateral avoidance manoeuvre around an obstacle (O) when the relativedistance between the motor vehicle (V) and an obstacle ahead liesbetween said intermediate value (d_(E)) and the second limit value(d_(Ecrit)).
 3. A system according to claim 1 or claim 2, for a motorvehicle (V) further provided with electrically-controlled steeringactuator means (8, 9); the system further including second detectormeans (17, 18) operable to provide electrical signals usable to evaluatethe viability of a possible avoidance path around an obstacle (O) aheadof the motor vehicle (V); the processing and control means (ECU) meansbeing further arranged to control the said steering actuator means (8,9)automatically in a predetermined manner to follow an avoidance patharound an obstacle (O) ahead if the relative distance between the motorvehicle (V) and said obstacle (O) has a value lying between saidintermediate value (d_(E)) and the second limit value (d_(Ecrit)).
 4. Asystem according to claim 3, wherein the processing and control means(ECU) are arranged to cause activation of the said brake actuator means(2-4) to effect an automatic emergency braking, when the relativedistance (d_(R)) lies between the above-said intermediate value (d_(E))and the second limit value (d_(Ecrit)) and said second detector means(17, 18) indicate the impossibility of performing a lateral avoidancepath around the obstacle (O).
 5. A system according to claim 3 or 4, inwhich the processing and control means (ECU) have associated therewiththird detector means (20) operable to provide signals indicating thepresence, the distance and the relative speed of vehicles overtaking themotor vehicle (V) from behind, and the said processing and control means(ECU) are also arranged to activate the said braking actuator means(2-4) and/or the steering means (8, 9) in dependence on the distance andrelative speed of the vehicles overtaking the motor vehicle (V) frombehind.
 6. A system according to claim 1, for a vehicle provided withfurther detector means (11, 12) for detecting the position of the brakecontrol pedal and the accelerator pedal, the said processing and controlmeans (ECU) being connected to the said further detector means (11, 12)and being arranged to interrupt the control of the longitudinal speed ofthe motor vehicle (V) when one of the said pedals is actuated.
 7. Asystem according to claim 1, in which the said feedback control means(32) are of proportional-integral type and the said compensation signal(a_(xcomp)) is essentially proportional to the integral of thedifference between the relative acceleration (a_(xref)) and theinstantaneous longitudinal acceleration (a_(F)) of the motor vehicle(V).
 8. A system according to any preceding claim for a motor vehicle(V) provided with electrically-controlled steering actuator means (8,9); the system further comprising fourth detector means (16) operable toprovide signals usable to identify the instantaneous position of themotor vehicle (V) relative to detectable demarcation means which delimitor define the road lane in which the motor vehicle (V) is travelling;the said processing and control means (ECU) being connected to the saidfourth detector means (16) and arranged to determine the instantaneousposition of the motor vehicle (V) relative to the said demarcationmeans; and control the said actuator means (8, 9) in a predeterminedmanner in such a way that the motor vehicle (V) continues to proceedwithin the said road lane.
 9. A system according to claim 8, for a motorvehicle (V) with a steering column (6) which has an associated sensormeans (10) operable to provide signals indicative of the torque appliedto this column (6) by the driver, and in which there are provided sensormeans (13) for detecting activation of the direction indicators; saidprocessing and control means (ECU) being arranged to reduce the weightof the control action of the said steering actuator means (8, 9) whenthe driver applies to the steering column (6) a torque greater than apredetermined value and/or to interrupt the said control action when thedriver activates a direction indicator.
 10. A system according to claim8 or claim 9, including further detector means (17; 18) operable toprovide signals able to allow a monitoring of the traffic to the sidesand rear of the motor vehicle (V), and in which the said processing andcontrol means (ECU) are further arranged to pilot the steering actuatormeans (8, 9) in such a way as to apply to the steering column aresisting torque when the driver tends to displace the vehicle laterallywhilst the signals provided by the said further detector means (17, 18)are indicative of a situation which could lead to a collision of themotor vehicle (V) with other overtaking motor vehicles or with lateralobstacles.